High power laser imaging is increasingly employed in modern printing operations. One example of a laser imaging technique utilized in these operations is offset lithography. In a typical lithographic process, a printing plate (e.g., a flat plate, an outer surface of a cylinder, belt) can be configured with “image regions” formed of, for example, hydrophobic and oleophilic material, and “non-image regions” formed of a hydrophilic material. Such image regions correspond to areas on a print media that are occupied by a printing or a marking material such as ink, whereas the non-image regions correspond to the areas on the print media not occupied by the marking material.
Variable data lithography (also referred to as digital lithography or digital offset) utilized in printing processes typically begins with a fountain solution that dampens an imaging plate (e.g., metal, silicone) on an imaging member (e.g., drum, cylinder, belt). The fountain solution forms a film on the imaging plate that may be about one (1) micron thick or less. The imaging member rotates to an “exposure” station where a high power laser imaging module (LIM) removes the fountain solution at the locations of the imaging plate where the image pixels are to be formed. This forms a fountain solution based ‘latent image’. The drum then further rotates to a ‘development’ station where lithographic-like ink may be brought into contact with the fountain solution based ‘latent image’ and ink ‘develops’ onto the places where the laser has removed the fountain solution. The drum then rotates to a transfer station where the ink is transferred to an offset blanket cylinder and then to print media such as paper.
A LIM that forms the latent image may include one or more lasers that work with one or more optical components to direct the laser onto the printing plate. Known approaches use a bar laser having a series of linearly arranged emitters which emit laser beams substantially in parallel that are superimposed on a grating light valve spatial light modulator (SLM) having a plurality of micro-lenses arranged in the corresponding relationship to the emitters of the bar laser. See, for example, U.S. Pat. No. 6,611,382. The laser provides constant illumination to the mirror array. The mirror array may deflect individual micro-mirrors to form the pixels on an image plane to pixel-wise evaporate the fountain solution on the silicone plate. If a pixel is not to be turned on, the mirrors for that pixel deflect such that the laser illumination for that pixel does not hit the imaging plate.
High power illuminators are needed for applications like 2D and 3D printing and engraving where light from the illuminators are incident on a rectangular pixelated SLM, like a Digital Light Processing (DLP) chip or Digital Micromirror Device (DMD). Achieving high laser power (e.g., 50 W up to 400 W) required to sufficiently light rectangular pixelated SLMs is difficult and expensive for a single laser device.